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United States Patent |
5,620,499
|
Farley
|
April 15, 1997
|
Chemical dispensing device and method
Abstract
The present invention is a device and method for selectively dispensing at
least one target compound into a selected environment. A target compound
is dissolved within an elastomer compound in a concentration that
supersaturates the elastomer compound. The elastomer compound is then
shaped into a selected form that is conducive to placement within the
selected environment. The target compound within the elastomer compound
begins to bloom to the surface of the elastomer compound where it is
exposed to the surrounding environment. The bloom of the target compound
into the surrounding environment continues until the concentration of the
target compound within the elastomer compound reaches its saturation
point. As such, the duration of the bloom of the target compound from the
elastomer compound can be regulated by the concentration of the target
compound within the elastomer compound, the volume of the elastomer
compound and the surface area of the elastomer compound.
Inventors:
|
Farley; James J. (505 E. Lancaster Ave., Apt. 412, St. David, PA 19087)
|
Appl. No.:
|
373890 |
Filed:
|
January 17, 1995 |
Current U.S. Class: |
71/64.11; 47/48.5; 71/64.13; 71/900 |
Intern'l Class: |
C05G 005/00 |
Field of Search: |
47/48.5,62,64
71/11,69.11,64.13,900
|
References Cited
U.S. Patent Documents
1554865 | Oct., 1925 | Magoon | 47/48.
|
2956073 | Oct., 1960 | Whetstone | 260/461.
|
3116201 | Dec., 1963 | Whetstone | 167/22.
|
3276857 | Oct., 1966 | Stansbury | 71/64.
|
3320695 | May., 1967 | Moore, Jr. | 47/9.
|
3336129 | Aug., 1967 | Herrett | 71/92.
|
3336155 | Aug., 1967 | Rowe | 117/100.
|
3417181 | Dec., 1968 | Cardarelli | 424/229.
|
3426473 | Feb., 1969 | Cardarelli | 43/131.
|
3520651 | Jul., 1970 | Philen | 23/50.
|
3590119 | Jun., 1971 | Cardarelli | 424/22.
|
3639583 | Feb., 1972 | Cardarelli | 424/125.
|
3705938 | Dec., 1972 | Hyman | 424/19.
|
3748115 | Jul., 1973 | Sommer | 71/64.
|
3805447 | Apr., 1974 | Rion | 47/9.
|
3851053 | Nov., 1974 | Cardarelli | 424/78.
|
3864468 | Feb., 1975 | Hyman | 424/16.
|
3961628 | Jun., 1976 | Arnold | 128/260.
|
4010141 | Mar., 1977 | Onozuka | 269/45.
|
4012221 | Mar., 1977 | Walker | 71/66.
|
4012497 | Mar., 1977 | Schopflin | 424/22.
|
4021965 | May., 1977 | Norris | 47/48.
|
4023955 | May., 1977 | Mueller | 71/64.
|
4034508 | Jul., 1977 | Dedolph | 47/84.
|
4051628 | Oct., 1977 | Knapp et al. | 47/48.
|
4063919 | Dec., 1977 | Grano, Jr. | 71/11.
|
4166111 | Aug., 1979 | Cardarelli | 424/78.
|
4166340 | Sep., 1979 | Pluenneke | 47/58.
|
4224048 | Sep., 1980 | Pendergast | 47/48.
|
4228614 | Oct., 1980 | Cardarelli | 43/131.
|
4237114 | Dec., 1980 | Cardarelli | 424/78.
|
4241537 | Dec., 1980 | Wood | 47/56.
|
4299613 | Nov., 1981 | Cardarelli | 71/64.
|
4344431 | Aug., 1982 | Yolles | 424/425.
|
4400374 | Aug., 1983 | Cardarelli | 424/78.
|
4404360 | Sep., 1983 | Cardarelli | 71/117.
|
4422990 | Dec., 1983 | Armstrong | 47/74.
|
4435180 | Mar., 1984 | Leeper | 604/896.
|
4554113 | Nov., 1985 | Chakra et al. | 423/300.
|
4581846 | Apr., 1986 | Stensaas | 71/64.
|
4983390 | Jan., 1991 | Levy | 71/3.
|
4988377 | Jan., 1991 | Manalastas et al. | 71/28.
|
5105577 | Apr., 1992 | Hedges | 47/9.
|
5162052 | Nov., 1992 | Hoffmann et al. | 47/48.
|
5181952 | Jan., 1993 | Burton et al. | 71/64.
|
Foreign Patent Documents |
3530297 | Feb., 1987 | DE | 71/64.
|
3638039 | May., 1988 | DE | 71/64.
|
63-317023 | Dec., 1988 | JP | 47/64.
|
3191720 | Aug., 1991 | JP | 47/64.
|
Other References
The Condensed Chemical Dictionary (Eighth Edition) Van Nostraad Reinhold
Company, pp. 71, 72, 388.
|
Primary Examiner: Lander; Ferris
Attorney, Agent or Firm: LaMorte & Associates
Parent Case Text
This is a continuation of application Ser. No. 07/990,281, filed on Dec.
14, 1992, entitled CHEMICAL DISPENSING DEVICE AND METHOD and now abandoned
.
Claims
What is claimed is:
1. A device for dispensing at least one fertilizer compound into a
surrounding environment over a period of time, comprising:
a homogenous, substantially water insoluble elastomer compound shaped into
a selected form, said elastomer compound including said at least one
fertilizer compound that is dissolved within said elastomer compound in a
concentration in excess of the solubility of said at least one fertilizer
compound at ambient temperature and pressure, wherein said at least one
fertilizer compound precipitates out of solution and migrates to an
external surface of said selected form, at a predetermined rate for said
period of time, thereby being dispensed into the said surrounding
environment in a controlled manner.
2. The device according to claim 1, wherein a secondary compound is
included within said elastomer compound in a concentration in excess of
the solubility of said secondary compound at ambient temperature and
pressure, wherein said secondary compound readily precipitates out of
solution and migrates to said external surface of said selected form and
promotes the bloom of said at least one fertilizer compound to said
external surface.
3. The device according to claim 1, wherein said elastomer compound
includes a rubber polymer selected from a group consisting of natural
rubber, isoprene rubber, butadiene rubber, chloroprene rubber,
isobutylene-isoprene rubber, nitrile-butadiene rubber, styrene-butadiene
rubber, ethylene-propylene copolymer, ethylene-propylene-diene terpolymer
and silicone rubber.
4. The device according to claim 2, wherein said elastomer compound
includes natural rubber and said secondary compound includes paraffin.
5. The device according to claim 1, wherein said selected form is an
elongated flexible strip which can be readily laid upon the ground
proximate plants in need of said at least one fertilizer compound.
6. The device according to claim 5, wherein said elongated flexible strip
includes a generally star-shaped cross-sectional profile to increase the
surface area along said flexible strip.
7. The device according to claim 1, wherein said at least one fertilizer
compound is present in a predetermined concentration, within said
elastomer compound, wherein said at least one fertilizer compound
precipitates out of solution with said elastomer compound and migrates to
said external surface of said selected form for a selected period of time.
8. The device according to claim 7, wherein said elastomer compound is
capable of being placed proximate plants in need of said at least one
fertilizer compound and wherein said selected period of time corresponds
to a growing period of said plants.
9. The device according to claim 1, wherein said elastomer compound is
cured.
10. The device according to claim 1, wherein said elastomer compound
includes a rubber polymer, an inert filler, at least one fertilizer
compound, a vulcanization agent, an accelerator and an antioxidant.
11. The device according to claim 1, wherein said elastomer compound
includes between 35% and 65% natural rubber, between 20% and 45% clay and
between 3% to 6% of said at least one fertilizer compound, whereby said at
least one fertilizer compound supersaturates said elastomer compound and
blooms out of the elastomer compound.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an elastomer compound used to slowly
dispense a fertilizer compound or other desired substance into a targeted
environment over a period of time. More particularly, the present
invention relates to such elastomer compounds where the desired substance
is dissolved within the elastomer compound, at a supersaturated
concentration, causing the desired substance to slowly bloom to the
surface of the elastomer compound and be dispensed into the surrounding
environment.
2. Description of the Prior Art
Bloom is a term of art in elastomers that refers to the migration of a
liquid or solid material from the composition of the elastomer to the
surface of the elastomer. Bloom is caused when a dissolved ingredient is
added to the elastomer compound recipe in a concentration that is in
excess of its solubility. In such a situation, if the conditions for
crystallization of the supersaturated ingredient are more favorable in the
presence of air than within the body of the elastomer, then the
supersaturated ingredient will separate out of the elastomer compound and
crystallize at the surface of the polymer as it contacts the surrounding
air. The change in the saturation concentration gradient created by the
surface crystallization causes the supersaturated ingredient to migrate
from within the elastomer compound toward the exterior surfaces of the
elastomer compound. The bloom of the supersaturated ingredient will
continue over time until the concentration of the blooming ingredient
within the elastomer compound falls to a concentration corresponding to
the saturation point of the elastomer compound. Bloom ceases when the
concentration of the migrating substance in the elastomer compound becomes
equal to its solubility at a given temperature.
The slow dispensing of a chemical compound, over a prolonged period of
time, is a useful process in many industries. One of the most obvious of
these industries is that of agriculture. Dispensing fertilizers and/or
pesticides on plants is often an expensive and labor intensive operation.
Additionally, conventional applications of fertilizer and pesticides must
be repeated because the potency of such compounds is often time sensitive.
Furthermore, environmental factors such as rain may wash such compounds
away from the plants before they have had an opportunity to perform their
intended function. Additionally, too much fertilizer or pesticide may have
an adverse effect on plants by causing fertilizer burn or adding
unacceptable levels of poisons to the fruit born by such plants.
In an attempt to reduce the time and labor involved with dispensing
fertilizer and pesticides to plants, the prior art has seen the
development of slow dispensing devices, whereby upon one application,
small amounts of fertilizer or pesticides are made available to plants
over an extended period of time. In the prior art, such slow dispensing
devices typically include a biodegradable material impregnated with a
fertilizer or pesticide product. As the biodegradable material decomposes,
the fertilizer and/or pesticide is released into the surrounding soil.
Such prior art devices are exemplified by U.S. Pat. No. 3,320,695 to
Moore, Jr., entitled DEGRADABLE POLYOLEFIN MULCHING FILM, U.S. Pat. No.
1,554,865 to Magoon, entitled DEVICE FOR TREATING SOIL and U.S. Pat. No.
4,063,919 to Grano, Jr., entitled FERTILIZER RODS.
The problems associated with such biodegradable fertilizer dispensing
devices is that they are time consuming and labor intensive to install
around plants. Furthermore, the amount of fertilizer or pesticide released
by such devices is dependent entirely upon the environment in which they
contact. For instance, if such devices were positioned in rich soil that
had a high moisture content and a high bacterial presence, the prior art
devices would decompose very rapidly and the fertilizer or pesticide
released would not last throughout the entire growing season. Adversely,
if such devices were positioned on dry soil with a very low moisture
content and bacterial presence, the prior art devices may not adequately
decompose and therefore may not properly dispense the fertilizer or
pesticide.
In other prior art products, the osmotic effect of water passing through a
fertilizer or pesticide containing medium is used to dispense the
fertilizer or pesticide around desired plants. One such prior art device
is taught by U.S. Pat. No. 4,224,048 to Pendergast, entitled OSMOTIC
FERTILIZER PRODUCT AND FERTILIZATION METHOD. In the Pendergast patent, a
fertilizer is shown impregnated within a water swellable polymer. The
polymer absorbs water administered to the plant, dilutes fertilizer into
the water and passes the water/fertilizer solution on to the plant with a
controlled capillary action. The disadvantage of this design is that the
water swellable polymer must be buried under the soil near each plant. For
this reason, the application of the water swellable polymer is highly
labor intensive. Additionally, with the use of a water swellable polymer,
the dispensing of fertilizer is directly proportional to the moisture
content of the soil. If the moisture content is high, osmosis occurs and
large amounts of fertilizer are released. Adversely, if the soil has a
very low moisture content, almost no fertilizer is released to the plant.
In U.S. Pat. No. 5,105,577 to Hedges, entitled ARTIFICIAL MULCH CHIPS, a
thermoplastic material is shown with a textured surface. The thermoplastic
material is then coated with an active ingredient, such as an insecticide,
and is thrown upon the soil in the region of a garden. Once in the garden,
the effects of wind and water cause diffusion of the active ingredient
into the surrounding environment. No mechanism is provided to control the
rate of diffusion of the active ingredient over time.
In U.S. Pat. No. 4,166,340 to Pluenneke, entitled POT LINING METHOD WITH
RECLAIMED TIRE FIBERS, a polymer is used to enhance the quality of soil
without the addition of a fertilizer compound. In the Pluenneke patent,
shreds of an automotive tire are used in the bottom of a potted plant. The
tire pieces provide good drainage characteristics and provide
micronutrients of sulphur, iron, zinc and manganese to the plant. The tire
pieces must be buried proximate the roots of a plant, as such the process
is highly time consuming and labor intensive.
Although the prior art does show the use of various elastomer products in
the controlled dispensing of fertilizers and pesticides, the prior art
fails to show fertilizers or pesticides dissolved within the elastomer
such that the added fertilizer or pesticide supersaturates the elastomer
compound and blooms to the exterior of the elastomer over a known period
of time. Such a migration of fertilizer or pesticide to the exterior of
the elastomer compound is not dependent upon available moisture in the
soil or the bacterial content of the soil. Consequently, fertilizer or
pesticide can be slowly and consistently dispensed over a period of time
regardless of the environment surrounding the plant.
It is a further object of the present invention to produce a product that
can be administered around plants above the soil, thereby reducing the
labor involved in supplying fertilizers to plants.
SUMMARY OF THE INVENTION
The present invention is a device and method for selectively dispensing at
least one target compound into a selected environment. A target compound
is dissolved within an elastomer compound in a concentration that
supersaturates the elastomer compound. The elastomer compound is then
shaped into a form that is conducive to placement within the selected
environment. The target compound within the elastomer compound begins to
bloom to the exterior surfaces of the elastomer compound where it is
exposed to the surrounding environment. The bloom of the target compound
into the surrounding environment continues until the concentration of the
target compound within the elastomer compound reaches its saturation
point. As such, the duration of the blooming of the target compound from
the elastomer compound can be regulated by the concentration of the target
compound within the elastomer compound, the volume of the elastomer
compound and the surface area of the elastomer compound.
In one preferred embodiment, the present invention device and method can be
used to dispense fertilizer to plants. In such an application, various
fertilizer compounds can be dissolved within an elastomer compound. The
elastomer compound can then be extruded, molded or otherwise shaped into
strips which can be placed on the ground near plants. The fertilizer
compounds will bloom from the strips and will pass into the soil where
they are absorbed by the roots of the plants. The strips can be
manufactured so that the bloom of the fertilizer compounds from the strips
will last throughout the growing season of the plants, thereby slowly
dispensing fertilizer to the plants regardless of soil conditions.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more fully understood by referring to the following
detailed specification, the above background and the claims set forth
herein, when taken in conjunction with the drawings appended hereto,
wherein;
FIG. 1 shows a perspective view of one preferred embodiment of the present
invention, shown in conjunction with plants to facilitate discussion and
consideration; and
FIG. 2 shows a cross-sectional view of one preferred embodiment of the
present invention shown in conjunction with a plant to help illustrate
operation.
DETAILED DESCRIPTION OF THE DRAWINGS
Although the present invention can be used in many different applications
where it is desired to dispense a chemical compound in a controlled manner
over an extended period of time, it is especially suitable for use in
dispensing fertilizers in agriculture. Accordingly, the present invention
will be described in connection with the controlled application of
fertilizers in an agricultural environment.
The phenomenon of bloom can be produced in a variety of natural and
synthetic elastomers. To create bloom within an elastomer, a chemical or
chemical compound that is soluble within the base elastomer must be added
to the elastomer compound in a concentration that supersaturates the
elastomer compound. Additionally, in order for bloom to occur, the added
chemical or chemical compound must have the characteristic of
precipitating out of solution more energetically in the presence of air
than within the body of the elastomer compound. If both criteria are
present, the chemical or chemical compound dissolved in the elastomer
formulation will slowly separate from solution at the surface of the
elastomer compound. The resulting change in the concentration gradient of
the dissolved chemical, causes the dissolved chemical or chemical compound
to actively migrate toward the exterior surfaces of the elastomer. The
amount of material that eventually migrates to the surfaces of the
elastomer compound is controlled by the amount of oversaturation, the
volume of the elastomer compound and the surface area of the elastomer
compound. As such, the bloom of a dissolved chemical or chemical compound
from the elastomer will continue until the concentration of the blooming
material within the elastomer compound falls to its saturation point. The
process of bloom is not instantaneous. Rather, depending upon such
variables as the type of elastomer, surface area, volume and degree of
supersaturation, bloom may occur within a period of time from hours to
years before an equilibrium within the elastomer compound is finally
achieved.
The phenomenon of bloom can be created in many types of natural and
synthetic elastomers. Such elastomers include, but are not limited to,
natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR),
chloroprene rubber (CR), isobutylene-isoprene rubber (IIR),
nitrile-butadiene rubber (NBR), butadiene-acrylonitrile rubber,
styrene-butadiene rubber (SBR), ethylene-propylene copolymer (EPR),
ethylene-propylene-diene terpolymer (EPDM) and silicone rubbers. Although
any of these elastomers may be used in forming the present invention, the
present invention is preferably formed utilizing natural rubber. Natural
rubber is a preferred embodiment because it is readily shaped, has a high
susceptibility to bloom and is soluble with many different types of
commercially available fertilizers. Referring to Table 1 below, a
preferred embodiment for the present invention rubber compound recipe is
shown.
TABLE 1
______________________________________
PERCENTAGE
INGREDIENT BY WEIGHT
______________________________________
Natural Rubber 35.0-65.0
Clay 20.0-45.0
Processing Oil 0.0-05.0
Colorant 0.0-05.0
Fertilizer 3.0-06.0
Sulfur 0.05-1.0
Zinc dimethyl dithiocarbamate
1.5-03.0
2-mercaptobenzothiazole
1.0-03.0
Antioxidant 0.0-01.0
Paraffin 0.0-04.0
______________________________________
The fertilizer of Table 1 can be any commercially available fertilizer
chemical or chemical compound. The selection of the fertilizer is
dependent upon the solubility of that fertilizer in the remainder of the
rubber compound recipe. As such, it will be understood that different
fertilizers may be used as the rubber compound recipe is varied, because
different fertilizers are more highly soluble in different recipes. Many
commercially available fertilizer compounds are soluble in natural rubber
compounds. Such fertilizer compounds include primary nutrients such as
nitrogen, phosphorus and potassium, secondary nutrients such as calcium
and magnesium and micronutrients such as iron, manganese, copper, zinc,
boron and molybdenum. Common fertilizer compounds such as ammonium nitrate
and monoammonium phosphate have been found to be soluble in varying
degrees in the natural rubber compound recipe of Table 1. As such, the
amount of fertilizer added to the rubber compound recipe depends upon the
fertilizer chosen.
As has been previously described, in order to facilitate the phenomenon of
bloom, the compound that is blooming has to be added to the rubber
formulation in a concentration that supersaturates the formulation. In the
present invention, it is desired to have the fertilizer to bloom out of
the rubber formulation. As such, the fertilizer must be added to the
rubber compound recipe in a concentration that supersaturates the rubber
formulation. As will be recognized by a person skilled in the art, the
solubility of one compound into another is typically temperature
dependent. As such, the amount of fertilizer added to the rubber compound
recipe will depend upon the temperature of the formulation during mixing.
Since it is desirable to supersaturate the rubber compound recipe with the
added fertilizer, it is desirable to mix the fertilizer into the rubber
compound recipe at a relatively high processing temperature, thereby
increasing the degree of supersaturation available in the final compound.
However, the processing temperature during mixing should not be high
enough to cause any curing of the formulation.
The clay of Table 1 can be any clay additive conventionally added to
natural rubber compounds. Such clays are well known in the art and are
added to natural rubber compounds to increase abrasion resistance,
increase tensile strength and increase stiffness. Other well known
materials, such as fine particle zinc oxides, calcium carbonates, calcium
silicates, amorphous hydrated silicon dioxide, pure silicon dioxides and
fine-particle magnesium carbonate, barium sulfate or carbon black can also
be used in combination with, or in place of, the preferred clay additive.
The processing oil of Table 1 is also a well known additive to natural
rubber compounds. Processing oils of many different types are
conventionally used in rubber compound recipes to decrease viscosity of
the compound, aid in the dispersion of fillers, reduce calendar shrinkage
and/or provide lubrication to aid in extrusion or molding of the compound.
The sulfur of Table 1 is used as the vulcanizing agent in curing the rubber
compound. The use of sulfur as a vulcanizing agent is extremely well known
and practiced in the art of natural rubber compounds. As the vulcanizing
agent, the sulfur cross links the various polymer chains within the
natural rubber creating the elastomer. Many natural rubber compounds
require a variety of operations that produce and require heat, such as
mixing, extruding, calendaring, molding and the like. As such, it is
desirable not to have an appreciable amount of polymer cross-linking to be
established before these operations are performed. To prevent the added
sulfur of Table 1 from causing premature polymer cross-linking, a delayed
action accelerator is added to the present invention natural rubber
compound.
In the rubber compound recipe of Table 1, the accelerator used is zinc
dimethyl dithiocarbamate in combination with 2-mercaptobenzothiazole
(MBT). It should be understood that either accelerator can be used by
itself. Similarly, any other well known accelerator conventionally used in
curing natural rubber, such as bis (2,2-benzothiazolyl) disulfide (MBTS),
benzothiazolesulfenamides, 2-(4-morpholinylthio)benzothiazole and the like
can also be used.
It should be understood that if a chosen fertilizer compound does not
rapidly dissolve within the rubber compound recipe of Table 1, a retarding
agent, sometimes called a prevulcanization inhibitor, may be added to the
rubber compound recipe to slow the vulcanization reaction. Such retardants
can prevent vulcanization of the rubber compound mixing, calendaring and
other processing steps, thereby providing the added fertilizer with
additional time to dissolve within the rubber compound. The retardants
used can be any conventional retardant used in natural rubber compounds
such as N-(cyclohexylthio)phtalimide (CTP), sulfonamide derivatives,
salicylic acid or the like.
In accordance with Table 1, an antioxidant is added to the natural rubber
compound. When natural rubber is harvested, it contains natural
antioxidants, proteins and complex phenols that protect the rubber from
deterioration over time. These natural protectants are destroyed during
vulcanization. As such, synthetic protectants are added to the rubber
compound recipe to ensure an adequate service life in the cured rubber.
There are many antioxidants conventionally used in association with
natural rubber. Any such known antioxidant may be used in the present
invention rubber compound recipe.
A colorant may be added to the rubber compound recipe in accordance with
the listing in Table 1. The colorant added controls the color of the final
rubber product. For example, black colorants can be used if it is
desirable to have a black rubber product. Many black colorants are known
and have been widely used in the automotive tire industry. A common
colorant is carbon black, however any other known colorant, for any color,
may also be used.
Paraffin may be added to the rubber compound recipe of Table 1 as a
precipitating agent. Paraffin dissolves in natural rubber and readily
blooms from the rubber if added to the rubber in a supersaturated
concentration. The bloom of the paraffin from the rubber compound promotes
the bloom of the fertilizer from the rubber compound. Furthermore, the
migration of paraffin to the surface of the rubber compound during bloom,
helps in the migration of the added fertilizer to the surface of the
rubber compound. The addition of paraffin within the rubber compound also
reduces the saturation point of the rubber compound. As such, a
supersaturation of fertilizer can be more readily achieved.
It will be understood that the rubber compound recipe set forth in Table 1
is merely exemplary and other recipes and/or other concentrations can be
used provided the added fertilizer supersaturates the resulting rubber
compound. Additionally, other ingredients such as stabilizers, softeners,
extenders, stiffeners, bonding agents and the like may also be added to
the rubber compound recipe in order to produce a final rubber compound
with desired physical characteristics.
The rubber compound made from the recipe set forth in Table 1 can be
molded, extruded or otherwise worked into any size or shape. Referring to
FIG. 1, it can be seen that in one preferred embodiment, the rubber
compound can be extruded into long strips 10 which can be placed on the
surface of the soil 12 proximate the stems of targeted plants 14. Since
the rubber compound strips 10 can be made of a natural rubber compound,
the strips 10 can be made to be highly flexible. As such, the rubber
compound strips 10 can be placed upon the soil 12 in any desired
orientation including a path that would serpentine between targeted plants
14 as shown. It will be understood that the present invention rubber
compound need not be molded into long strips 10, as shown, but may be
molded into any desired shape or form. For instance, the present invention
rubber compound can be molded into ornamental designs that can be placed
in a garden. Alternatively, the rubber compound can be molded into
artificial mulch chips which can be placed throughout a garden or around
plants as part of landscaping. In an alternative embodiment, the rubber
compound can be molded into large flat sheets that can be placed
throughout a garden to help deter the growth of weeds.
Referring to FIG. 2, it can be seen that in the preferred embodiment, the
rubber compound strips 10 are molded to have a star-shaped cross-sectional
profile. Such a configuration is readily made using a star-shaped
extrusion die. By configuring the rubber compound strips 10 with a
star-shaped profile, the surface area of the rubber compound strips 10
that is exposed to the surrounding air can be increased.
As has been previously described, bloom will occur when a supersaturated
additive to an elastomer compound precipitates out of solution with the
elastomer compound more readily in the presence of air than within the
body of the elastomer. As such, it should be understood that the
phenomenon of bloom can be largely reduced or delayed by keeping the
supersaturated elastomer in an air free enclosure. Upon the extrusion of
the rubber compound strips 10, the strips 10 can be shrink wrapped in
cellophane or the like. Consequently, bloom can be substantially delayed
until the rubber compound strips 10 are purchased by a consumer and the
cellophane coating is removed, thereby exposing the surfaces of the strips
10 to air.
In FIG. 2 it can be seen that the fertilizer contained in the original
rubber compound recipe of Table 1, blooms to the surface of the rubber
compound strips 10. As the fertilizer blooms, it precipitates out of
solution and crystallizes on the surface of the rubber compound strips 10
so as to form a pellicle layer 20. Rain, irrigation water, wind and the
like then cause the crystallized fertilizer contained within the pellicle
layer 20 to flow onto the soil 12. Once the fertilizer is dispensed onto
the soil 12, the roots 22 of the targeted plants 14 can absorb the
fertilizer in the conventional manner as depicted by arrow 25.
The bloom of fertilizer will continue within the rubber compound strips 10
until the concentration of fertilizer within the rubber compound strips 10
reaches the saturation point and the rubber compound ceases to be
supersaturated with the added fertilizer. As has been previously
mentioned, rubber compounds can be formed so that bloom occurs from a
period of time from hours to years. In the preferred embodiment, the
concentration of fertilizer within the rubber compound is calculated so
that bloom will continue for a few months (i.e. the growing cycle of the
target plants 14). Consequently, small amounts of fertilizer will be
dispensed to the targeted plants 14 throughout the entire growing season
of the plants 14. As the growing season of the targeted plants 14 ends,
and the fertilizer reaches an equilibrium point within the rubber
compound, bloom ceases and the rubber compound strips 10 can be removed
and discarded.
For plants that require fertilizer year round, rubber compound strips 10
can be manufactured that last for a desired period (i.e. six months, one
year, etc.). As such, the rubber compound strips 10 can be replaced on an
annual or semi-annual basis. Additionally, different fertilizers can be
added to the rubber compound strips 10 for different seasons, thereby
allowing different fertilizers to be dispensed by periodically changing
the strips 10. The bloom of fertilizer from the present invention rubber
compound lasts as long as the fertilizer does not reach a saturation
equilibrium within the rubber compound. As such, bloom continues depending
upon the volume of rubber compound, concentration of fertilizer and
exposure of the rubber compound to air. Despite the long period of bloom,
the rate of bloom is not constant, but is rather exponential, being more
rapid at first and slowing over time. This complements agricultural plants
very well, where more fertilizer is needed during the initial growing
phase of the plants than is required during the later, maturing periods of
the plants. As such, the present invention strips 10 are best dispensed
during the growing phase of plants so that fertilizer can be provided
throughout the life of the plant in the needed proportions.
In the shown embodiment of FIG. 2, the star-shaped profile of the rubber
compound strips 10 increases the surface area of the strips 10. As such,
more of the rubber compound material is exposed to the surrounding air,
thereby increasing the rate of bloom and the volume of fertilizer
dispensed over time. It will therefore be understood that by changing the
shape of rubber compound strips 10, the rate of bloom can also be
controlled. As such, different shaped strips may be manufactured for
different types of plants, whereby the type of fertilizer, the
concentration of fertilizer, the volume of the rubber compound and the
shape of the extruded strips can be made to match the specific fertilizer
needs of differing plants.
Although the above described embodiment of the present invention rubber
compound is believed to represent the best mode of the present invention,
it will be understood that many described chemical components of the
rubber compound recipe have known functional equivalents. Additionally,
proportions used within the described recipe may be changed and
undescribed chemical compounds may be added to the rubber compound by a
person skilled in the art. All such modifications and additions are
intended to be covered by the scope of this invention as set forth in the
appended claims.
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